Transmission of pictures and views



c. A. SABBAH TRANSMISSION OF PICTURES AND VIEWS Filed. May 27, 1925 Inventor: Camille A.Sabbah,

nee. 11, 1923.

UNETED STATES PATENT OFFICE.

CAMILLE A. SABIBAH, OF SCHENECTADY, NEW YORK, ASSIGNOR'TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

TRANSMISSION OF PICTURES AND VIEWS.

Application filed May 27, 1925. Serial No. 33,270.

My invention relates to the electrical transmission of pictures and views. An object of my invention is the provision of improved method and means for the rapid transmission of still pictures and views and for the transmission of moving pictures and views: A further object of my invention is to provide apparatus for this purpose which shall have no moving material parts and which is thereby free from inertia efiects.

In accordance with my invention I project an image of the pictureor view to be transmitted on a plate or screen which has the property of reflecting electrons in proportion to its illumination and cause a cathode ray rapidly to scan the image so formed. As the ray moves over the image the number of electrons reflected varies with the illumination of the various portions of the image being dependent upon the coefiicient of electron reflection of each small unit area. A return path is provided for the reflected electrons and the resulting current variations after being amplified are adapted to be transmitted by wire or radio to a distant receivingEi station.

eferring to the drawing, Fig. 1 is a diagrammatic representation of one form of apparatus involving my invention; Fig. 2

shows one form of wave used for moving the cathode ray; Fig. 3 shows the spiral path which the cathode ra is caused to take, and Fig. 4is a modified orm of wave.

In Fig. 1 I have shown diagrammatically a cathode tube 1 having at one end the filament 2 which is adapted to be heated by the battery 3. In front of the filament 2 is the anode 4 connected with the filament through battery 5 and having a small opening therein.

through which the cathode ray is directed toward the transparent plate 6 at the opposite end of the tube. On the plate 6 is a thin semi-transparent film 7 of photoelectric substance, for example, caesium, sodium or potassium, such that the number of electrons reflected from a point thereof upon which the cathode ray is directed varies with the illumination of that point.

For the desired reflection of the electrons the resistance of the film is such that the time for the light quanta to knock out an electron is shorter than the time required for the plate to carry the electron away. A film of considerable resistance is required in order that enough time shall be given to electrons to be reflected by the action of the light quanta before they are conducted away to other parts of the film. At the same time it should be sufliciently conducting not to hold and accumulate a charge over a period greater than that during which the cathode ray scans the image so that the ray will not be seriously distorted. A film of any conducting metal can be made to have the desired degree of h gh resistance by making the thickness sutliciently small. For collecting the reflected electrons and returning them" to the anode,

I have shown a collector 8 having pointed electrodes 9 and a circuit connection through resistance 10 leading back to the anode 4. 7 It desired the collector may be made of thin widely spaced wire gauze. The film 7 is con nected through the battery 12 back to the anode 4. A suitable lens 14 is shown connected by a bellows 15 with the tube so that i it may be adjusted to produce a sharp image 16 on the plate 6 of the picture or view represented by the arrow 17.

Vvithin the tube 1 and arranged on opposite sides of the path of the cathode ray at a point preferably adjacent the anode are two pairs of spaced parallel plates 18 and 19, the one pair being placed at right angles to the other. As is well understood by those skilled 1n the art, it charges are given to these pairs 5 of plates the cathode ray which passes between the plates will be distorted or bent and that by suitably varying the charges on the two pairs of plates relative to each other the ray can be made to-follow any desired path. If the picture or View to be transmitted is' still, movement of the ray in scanning the image need only have such speed that the movement of the corresponding spot of light in the receiver may not be detected by the eye of the observer. For the transmissionof a moving picture or view the ray should scan the entire image at least sixteen to twenty times per second to prevent the effect of flickering of the transmitted picture.

Various methods may .be employed for varying the field between the plates 18 and the plates 19 to'cause the ray to cover the image on the plate 6 with the desired speed.

One arrangement whereby the plates 18 and 19 may be energized in a manner to cause the ray to travel in spirals such as shown in Fig. 3 at the desired rate is shown diagrammati cally in Fig. 1. A well known form of selfrectifying circuit is employed comprisin the two p iotrons 20 and 21. When the recti ying circuit is fed by the transformer 22 connected for example to a ten cycle source of alternating current, the current in the oscillation circuit 23, 24, 25, 26 may be of the form represented by 27 in Fig. 2, the high frequency oscillations being modulated by the ten cycle current. A winding 28 in inductive relation to the oscillation circuit is connected in circuit with an inductance 29 and resistance 30. One pair of plates, for example plates 18, is connected across the inductance 29, the other pair of plates is connected across the resistance 30. By this arrangement the currents traversing the two pairs of plates are substantially in quadrature with each other and each has the form illustrated by Fig. 2. The

resulting effect upon the cathode ray is to cause it to trace upon the film 7 of plate 6 spiral paths such as illustrated for example by 31 in Fig. 3. Every small unit area of the image on the plate is thus covered many times per second by the ray. At this point of the description it is desired to point out that the drawing is purely diagrammatic in character and that no attempt has been made therein to show the various parts in their true or relative proportions. Likewise in the diagrams forming Figs. 2 and 3, as well as Fig. 4 to be described hereinafter, the high frequency wave and the resulting pitch of the spiral 31 are not illustrative of actual conditions but rather have been shown having such values as is found most convenient in illustrating the idea.

The current impulses traversing the resist ance 10 as a result of the cathode ra scanning the image and the electrons being reflected from the film 7 of plate 6 may be transmitted to a distant station either by wire or by radio. Two amplifying pliotrons 32 and 33 are shown connected together by the transformer 34, the grid and filament of the first pliotron bein connected with the resistance 10 and the plate of the second pliotron being connected through the trans former'35 with a suitable wire or radio transmitting apparatus not shown.

' In using the apparatus, the ten cycle current supplied to the transformer 22 causes the cathode ray which is projected from the cathode 2 throu h the opening in the anode 4 to be deflecte and to trace spirals on the film 7, a complete spiral being traced during each of the intervals a--b, bc, c-d, and d-e of Fig. 2. At the same time, the image of the picture or view to be transmitted is being projected by the lens 14 upon the film 7 of plate 6. As the ray is rapidly moved over the image the number of electrons reflected from the film 7 at each instant will vary in accordance with the illumination of the particular point of the image engaged by the ray at that instant. The reflected electrons are collected by the electrodes 9 on collector 8 and returned to the anode 4 through resistance 10. Thus. the current through the resistance 10 is at any instant a measure of the illumination of the particular spot of the image upon which the cathode ray is falling at that instant and the resulting potential drop across the resistance after being amplified is transmitted by wire or radio to the receiving station.

The ray may be made narrow enough and the turns of the spiral close enough to produce a picture having the desired sharpness. The entire image is thus covered twice during each half wave of the ten cycle current. While I have used terms such as light and illumination in speaking of the image formed upon the plate 6, I desire it to be understood that I use these terms in their broadest sense to cover not-only the visible portions of the spectrum but also the invisible portions thereof since the material forming the film 7 can be selected so that it will respond to visible or invisible rays.-

Instead of causing the cathode ray to cover the image by tracing spirals upon the plate 6 it may be caused rapidl to sweep up and down over the plate whi e advancing back and forth across it, thus tracing a path after the fashion of that illustrated by the line 37 in Fig. 4. In this way the entire image is covered during. each horizontal traverse of the ray. For moving the ray in this manner the self-rectifying circuit illustrated may be dispensed with and one pair of deflecting plates may be connected to a source of sustained high frequency while the other pair of plates may be connected to a source of lower requency which may be of the order of sixteen or twenty cycles per second or higher if desired.

By whichever method the ray is moved, it will be noted that the apparatus includes no material moving parts and hence no inertia effects have to be considered. The only moving element is the cathode ray and this is adapted to respond instantly to the deflecting force.

For receiving the picture or view thus transmitted I may use a cathode raytube havin means similar to that already describe for moving the ray and in which the voltage between anode and cathode is caused to vary in accordance with the impulses received from the transmitting station. The ray in this case ma fall on a semi-transparent film of hosp orescent substance and the plate may e viewed through a suitable lens or eye piece.

Synchronization of the transmitting and receiving apparatus is obtained by employing oscillation circuits 23, 24,25 and 26 in the transmitter and the receiver having the same frequency and by slight manual variations in the constants of the circuit maintaining the exact synchronization'necessary to prevent distortion of the picture.

What I claim as new and desire to secure by Letters Patent of the United States, is:

l. The combination of a photoelectric film, means mounted on one side of said film for forming an image on said film, means mount ed on the other side of said film for projecting a cathode ray upon said film, and a transparent support for said film.

2. A picture transmitting apparatus including a transparent support, a light sensitive member mounted on said support, means for forming an image on said member, and means for causing a cathode ray to scan said member.

3. A picture transmitting apparatus including a transparent support, a light sensitive member mounted on said support, means for forming an image on said member, means for causing a cathode ray to scan said memher, and a collector provided with electrodes arranged to receive the electrons reflected from said light sensitive member.

4:. A picture transmitting apparatus including a transparent support, a light sensitive member mounted on said support, means for forming an image on said member, means for causing a cathode ray to scan said mem ber, a collector provided with a plurality of pointed electrodes arranged to receive the electrons reflected from said light sensitive member, and means for amplifying the current of said reflected electrons.

In Witness whereof, I have hereunto set my hand this 26th day of May, 1925.

CAMILLE A. SABBAH. 

